What is an overhead conveyor?
Overhead conveyors are what people are generally thinking about when they hear the word “conveyor”. One of the most common types of conveyor, an overhead conveyor is generally used in a production facility to move parts from one location to another. They take advantage of the generally unused vertical space above the working area. Using curved sections or even with elevators, they bring parts down to the level of operators and back up to higher elevations. Overhead conveyors can pass through production areas that humans can’t like through ovens and robot work cells.
From the days of Jervis B. Webb inventing the modern forged rivetless conveyor chain for the Ford Model T to the present day, Jervis Webb and now their integration partner, Ultimation Industries, have been the leading overhead conveyor manufacturers.
What type of overhead conveyor do I need?
Classification system for conveyor types
At Ultimation, we classify overhead conveyors according to these segments:
- Movement system – which can be hand pushed (simplest), motorized or power and free (motorized with two tracks). Click on hand push or Power and Free conveyor type here as each has their own web page
- Track style – which can be I-beam style tracks (typically 3″, 4″ or 6″ high carbon I-beams) or the Jervis Webb Unibilt enclosed track style
- Installation orientation – as you’d guess, most overhead conveyor systems are installed in an overhead orientation. But not always. When installed in an inverted (upside down) orientation, these same conveyor components can be used at floor level. For paint finishing systems it can be especially value to use an inverted conveyor system as the risk of dust, dirt or oil dripping from the conveyor onto the parts to be painted is removed.
The balance of the content on this page is explaining motorized overhead conveyors (sometimes call monorail conveyors) using both enclosed track and I-beam systems.
Enclosed Track Conveyor
Unibilt is the brand name for the Jervis Webb Enclosed Track Conveyor Systems. Simple in nature, the Unibilt system is modular and expandable from hand push systems to powered overhead conveyors to power and free systems. The Unibilt system consists of a full range of components that can achieve nearly any conveying task:
- Unibilt enclosed track is the starting point for the system. Available in various lengths and also in stainless steel, the Unibilt track system is the starting point for a motorized conveyor. Yokes are added at the ends of each section to enable easy mounting to the floor or roof supported steel support structures. Unibilt track is either welded together or bolted together. Horizontal curves enable to track to turn left and right, while vertical curves enable the track to go up and down. You can purchase track here
- Unibilt chain runs through the track. It’s unique configuration with side guide rollers enables very low friction and extremely long life. Chain is inserted into the track via a special piece of track which has a hinged opening which can open and close.
- Trolley attachments are added at the required spacing where the conveyor will carry its load. These attachments can be as close as 8″ apart, but are typically 16″ – 96″ depending on the parts the conveyor will carry. There is a vast range of different attachment types available. Some can be attached after the chain has been installed, some allow pivoting when the track is angled and going up or down a vertical curve. Some have spinners to allow the parts to rotate. You can see and purchase the available trolley and load attachments here
- The conveyor is motorized by adding a drive unit. The Unibilt drive unit includes an electric motor, gearbox (with various ratios available depending on the required feet per minute chain speed) and the necessary chain drive system to pull the main chain through the Unibilt track. Unibilt drives include a adjustable safety overload system with electric control. If for any reason the conveyor chain should ever jam, the Unibilt drive can be programmed (via PLC or a relay) to automatically shut down the conveyor once the force limit is reached. It’s common to add a variable frequency drive (VFD) to the electric motor. By changing the frequency of the AC power, the motor speed is adjusted within the range 15Hz (slowest) to 60Hz (full speed of the motor)
- Finally a take up is added. The purpose of the take up is to tension the chain, so it does not bunch up and so it runs smoothly in the track. Take ups are typically a curved section of 180 degrees track with a screw or air cylinder pushing the track outward to tension the chain.
Unibilt systems can handle individual loads up to 250 lbs. (115 kg), making them ideal for high-volume production runs or assembly operations. Regardless of size or the scope of the System, these easily installed conveyors provide a number of advantages including:
Design Flexibility: Use of universal link chain makes shorter radius curves and closer spacing of curve tangents possible, accommodating even the tightest of spaces.
Improved Work Environments: Enclosed track conveyor design helps prevent external contamination from reaching the chain or track bearing surfaces. Inverted system option also helps to confine dust, grease, and other potential contaminants from getting on the load or carrier, helping to keep both the workplace and product clean.
Modular Construction: Patented nested end yoke track connections increase ease of installation and help minimize downtime in the event of layout modification.
Design Options: Enclosed track overhead conveyor systems are designed to fit a variety of additional applications including: overhead power & free systems, over-n-under systems, inverted power & free systems, and hand-pushed trolley installations
Load limits for Unibilt enclosed track conveyors
Unibilt track systems should always be bolted or welded to appropriately sized steel support structures. Consult a civil engineer as required to calculate support steel requirements. Never bolt or attach Unibilt track to wood support structures.
The safe load limit of a Unibilt track and trolley system is dependent on 3 factors:
- Support steel load capacity
- Conveyor trolley load capacity. For Unibilt system, the maximum load for Unibilt trolley is 250 pounds per trolley. For higher loads, trolleys can be combined with a load bar
- Track load bearing capacity. This is dependent on the support centers that the track is attached by. For the Unbilit track system, these limits are:
- 471 pounds per linear foot when the track is supported on 5′ centers
- 273 pounds per linear foot when the track is supported on 6′ centers
- 115 pounds per linear foot when the track us supported on 8′ centers
- Do not exceed 8′ support centers
- The above values need to include weight of the track, weight of the trolley and any load bar, and the weight of the load carried
Unibeam overhead conveyors (I-beam monorail style)
Jervis B. Webb’s rugged line of Unibeam Overhead Trolley Conveyors are the finest quality 3” and 4” I-beam conveyor systems that use a rivetless chain available on the market. Unibeam conveyors are excellent for heavy-duty assembly line operations, manufacturing processing and paint finishing lines. Over 90 years experience goes into every product that Webb manufactures.
Unibeam overhead conveyors utilize I-beams for the track rather than the enclosed track used by the Unibilt components. I-beam conveyors are often used for heavier loads as the weight limits per trolley are substantially higher.
Unibeam Components Include:
- Tracks made from C-1045 steel — the best I-beam conveyor track available
- Trolleys forged from carbon steel and held together with a rugged two-bolt connection
- Traction Wheels made with retainer plate to contain wheels
- Roller Turns made with high carbon I-beam track and sealed-for-life rollers
- Drives that utilize rotary design and limit switch cut-off
- Take-ups with travel greater than 8”
- One piece oven expansion joints
- Capacity 3″ Trolley: 200 Lbs., 400 Lbs. with Load Bar
- Capacity 4″ Trolley: 400 Lbs., 800 Lbs. with Load Bar
- Optional 6″ Systems also available: For loads of 1,500 pounds up to 20,000 pounds using special load bar and trolley arrangements